The instant invention relates to an electronic apparatus for the measurement of systolic and diastolic blood pressures, including temperature indicator, timer, pulse rate calculator and memory.
There are two methods of blood pressure measurements of the human or animal subject; (1) the direct method which employs the insertion of a cannular probe into the blood vessel, while said probe is connected to a blood pressure measuring apparatus, and; (2) the indirect procedure, which is the most widely accepted method in clinical practice that utilizes the compression arm-cuff with the associated components. The latter senses for the "Korotkoff sounds" created by the acoustical turbulence of blood flow through the compressed semi-opened artery such as the brachial artery. When the brachial artery is fully compressed by the arm-cuff, there is no sound detected because of the absence of arterial blood flow below the fully occluded portion of the said compressed artery. As the arm-cuff pressure is gradually released from that state of compression and total arterial occlusion, each cardiac systole delivers an arterial pressure head force that becomes propagated through the semi-opened artery until the critical resistance exerted by the intravascular wall is exceeded by the said arterial pressure head force, at which instant, the first sharp "thud" sound of "Korotkoff" is detected, thereby determining the systolic reading in relation to the millimeters of Hg. of applied cuff pressure registered in the pressure gauge. As the compressed artery undergoes continuous gradual decompression, the "Korotkoff" sounds follow five phases of characteristically differential sounds; (1) first phase characterized by the aforementioned sharp "thud" sound; (2) a second phase characterized by blowing or swishing sounds; (3) a third phase characterized by a softer thud sound than phase 1; (4) a fourth phase with a soft and blowing sound that disappears and; (5) a fifth phase when the sounds completely disappear. The occurrence of the fifth phase is the commonly acceptable diastolic blood pressure reading in the cases wherein only one diastolic measurement is taken. The fourth phase is considered to have certain disadvantages when used to indicate the diastolic level.
The instant invention provides apparatus which permits much more rapid measurement of blood pressures and in which the subjective determinations of the auscultatory technique together with variations which may be due to the different hearing characteristics of administering personnel are entirely eliminated. The measurements with the apparatus of the instant invention are thus less subject to variations and may be made by persons without skill or training. The apparatus, however, is not unduly complicated, bulky, or expensive; and to the extent that it is somewhat more expensive than presently used blood pressure measurement apparatus, the expense is far more than justified by the saving in time of highly trained physicians and nurses.
The apparatus is contemplated primarily for use in the clinical measurement of blood pressure in connection with physical examinations or the like, but it may also be adapted to automatic measurement of blood pressure for purposes of research, automatic monitoring of hospital patients, or for use by athletes in stressed or unstressed condition.